Device for correcting last models



Dec. 7, 1943. 'o. s. PORTER EI'AL DEVICE FOR CORRECTING LAST MODELS 2 Sheets-Sheet 1 Filed June 26, 1941 Dec. 7, 1943. o. s. PORTER ETAL I I 2,336,033

DEVICE FOR CORRECTING LAST MODELS Filed June 26, 1941 2 Sheets-SheetB Patented Dec. 7, 1943 DEVICE FOR CORRECTING LAST MODELS Oscar S. Porter, Shrewsbury, and Leo A. Carroll,

Lynn, Mass., assignors to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application June 26, 1941, Serial No. 399,952

7 Claims.

'This invention relates to model making in connection with the manufacture of lasts and is disclosed herein with reference to an improved device for use in correcting th bottom profiles of last models.

Style and foot fitting standards require that there be no variation as to certain characteristics of lasts regardless of their size or width. For example, all lasts in a series of the same style should have the same heel height and toe spring. These requirements give rise to a difficulty in last making because of the well-known fact that the grading mechanism commonly used in last lathes is substantially pantographic in its action, multiplying all perpendicular distances from the grad ing axis by a factor which is constant through out the turning. This causes a variation in the bottom profile of an enlargement or diminution of the model as compared with that of the model. That is, the toe tip being substantially on the turning axis is reproduced correctly; but the heel drops a certain amount, and the ball drops (absolutely) more than any other point on the bottom since it is farther below the turning axis than any other point. I

The resulting variation in the bottom profile of the model is observable by holding the model with its forepart resting on a plane surface so that its heel height is correct or so that its forepart treads properly. In the first case, the variation is indicated by an exaggerated toe spring (the vertical distance from the tread surface to the toe tip). In the second case the variation is observed as an excessive heel height. Actually the total variation is a combination of one in the Wedge angle and another in the toe spring of the last model. To make a complete series of lasts, it is therefore common practice to provide a series of models in sufiicient number that the above-mentioned variation in lasts turned from the models will be negligible.

In making a model, it is customary to use a correct model in a last lathe to produce as accurately as possible by this method, considering the difiiculties outlined above, an approximate enlargement or diminution of the correct model. The approximate model is then itself corrected by a considerable amount of hand work includ ing the following procedure: a saw cut is made through the bottom surface of the model toward but not through its top surface along a section corresponding substantially to that where the waist measurement of the model is taken, that is, at the section of the model just behind the ball where its girth is a minimum. A similar cut is made in the model through the top of the cone, toward the bottom of the model but not through it, on a section which is substantially perpendicular to the bottom of the model at the forward edge of the heel plate or heel seat of a last corresponding to the model. The toe and heel portions of the model are thus partially separated from its mid portion and are capable of being moved, using the uncut sections of the model as hinges, so as to correct the toe spring and wedge angle.

Holes are next drilled transversely of the kerfs mentioned above to receive fastenings which upon being driven are intended to hold the toe and 1 heel portions of the model in their corrected relation with respect to the mid portion of the model. It is impracticable to maintain by hand the desired relation between the portions of the last when these holes are drilled, with the result that when a fastening is driven to correct the model, that part of the hole which is in one portion of the model is moved out of alignment with the other part of the hole in the other portion of the model, thus causing a binding action on the fastening which may prevent it from being driven to the extent necessary to effect the required correction of the model. Moreover, it is desirable that the movement of the toe and heel portions of the model necessary to make the corrections in question shall not result in their lateral surfaces adjacent to the kerfs becoming misaligned or discontinuous, since in such a case the swing of the model would be effected and the removal of material from the sides of the model necessary to make them smooth and continuous would reduce the size of the model in the area affected. This last-mentioned difficulty is minimized if the above-mentioned kerfs are made so that the bottoms of the kerfs are substantially parallel to the bottom of the model or, in other words, are perpendicular to the same given plane, but this result can not be obtained accurately or approximated consistently when, as is the common practice, the model is positioned with respect to the saw entirely by hand.

The present invention contemplates broadly the provision of a device for accurately controlling each of the above procedures, namely, the formation of kerfs in a model to be corrected, the bottoms of which are to be perpendicular to the same plane and parallel to the bottom of the model, the positioning and holding of the toe and heel portions of the model relatively to its mid portionsoas to provide the proper bottom profile.

and the fastening together of all the portions of the model in their corrected relation.

Accordingly, the invention provides an improved device for use in correcting a last model characterized by having means for positioning the model as it is presented to a saw in such a manner that the desired parallelism between the bottom of the model and the bottoms of kerfs made by the saw is attained. Such positioning of the model is effected, in connection with the use of a saw of the band type having a blade movable perpendicular to the table of the saw, by securing the model in the device or holder and by providing a guiding surface thereon adapted to rest on the table of the saw, the bottom of the model being perpendicular to the guiding surface of the holder. Thus, regardless of the angular relation of the planes of the kerfs'to each other, the bottoms of the kerfs will be parallel to the bottom of the model.

Another important feature provided by the invention consists in providing means in the device for relatively moving the toe, heel and mid portions of the model, which are partially separated from each other by the kerfs referred to above, to correct the bottom profile of the model and in providing means for holding these portions of the model in their corrected relation to facilitate both the gaging of the model in order to determine when the desired relation between parts of the model has been reached, and the final fastening together of the parts of the model in this relation.

Thus, the above-mentioned shortcomings of the prior methods of correcting models by hand are avoided by the use of the device of the present invention since the correct relation is maintained between the model and saw when the kerfs are made and also between the surfaces or parts of the model throughout each stage in the correction of the model.

The above and other objects and features of the invention will be better understood from the following description of an illustrative embodiment thereof taken in connection with the accompanying drawings, in which,

Fig. 1 is a view in perspective illustrating a last model correcting device embodying the invention and its use in forming kerfs in the model;

Fig. 2 is a. sectional plan view of the device illustrating its use in correcting the wedge angle and toe spring of a model; and

Fig. 3 is a sectional view on a reduced scale taken on the line III]II of Fig. 2.

The illustrated device comprises a frame having parallel upper and lower members ll), l2, and vertically disposed struts l4, I6 and I8, the ends of the struts being rigidly connected by screws 20 to the members if! and I2. The lower surface of the member l2 acts as a guiding surface for the device and is adapted to rest on a saw table 22 through which a saw blade 24 of the band type is adapted to move perpendicular to the table 22.

A last model 26 to be corrected is secured in the device as will be described below so that when the model is presented to the saw 24, with the member l2 then resting on the table 22, the bottom of the kerf made by the saw will be substantially parallel to the bottom of the model. Each of the members l0, I2, has a central run extending heightwise of the mid portion of the model, this run of the member ID being provided with a row of spaced holes 21 any one of which is adapted to receive a rod 28 having a knurled head 30 on its upper end, the lower end of the model mounted on the rod 28 are substantially parallel to the direction of movement of the saw blade 24. Hence, the bottoms of kerfs made by the saw blade when the 'device is resting on the table 22 will be located in a direction extending widthwise or transversely of the model, as viewed in Figs. 1 and 2, and they will be parallel to the bottom surface of the model widthwise of said model. Moreover, since the saw 24 moves in a path perpendicular to the guiding surface provided by the member [2, the bottoms of the'kerfs will be perpendicular to the guiding surface or the plane thereof, this surface, as pointed out above, being perpendicular to the rod 28 and, hence, perpendicular to the bottom of the model mounted on the rod since the jig hole in the model is parallel to its bottom surface. A clamp 32 is arranged to cooperate with the rod 28 to hold the mid portion of the model firmly in the illustrated device. The clamp 32 extends lengthwise of the ridge of the cone of the model, and carries pads 34 adjacent to its ends which are adapted to engage the ridge of the cone of the model at spaced points. The clamp 32 is mounted on a pair of guide rods 36 (Fig. 3) the outer ends of which are connected by a plate 38, the rods being mounted to slide lengthwise thereof in the strut IS. The clamp 32 is moved toward and away from the model by a screw 40 which is threaded in the strut IS, the inner end of the screw 40 being adapted to rotate freely in the clamp. Assuming now that a model to be corrected has been properly drilled as described above to receive the rod 28, the model is mounted on the rod and the screw 40 is operated to clamp the model securely in the device. The model is next presented to the saw 24 so as to form a kerf 42, located before the mid portion of the model substantially where its waist measurement is taken (section of minimum girth), and extending transversely and heightwise of the model. This kerf terminates short of the upper surface of the model so as partially to separate the toe end of the model from the mid portion thereof and to permit the toe portion of the model to be moved, using the narrow and springy uncut section of the model as a hinge, in order to correct the toe spring of the model. A similar kerf 44, to permit a correction to be made in the wedge angle of the model, is out toward (but not through) the bottom surface of the model through the top of the cone, the plane of this kerf passing through the bottom of the model substantially perpendicular thereto along a line corresponding to the forward edge of the heel plate or heel seat of a last corresponding to the model. As clearly shown in the drawings, the central runs of the members 10 and I2 are so shaped and arranged as to occupy only a part of the space included between the planes of the kerfs 42 and 44, thereby to permit unobstructed access to the saw 24 of the portions of the model to be cut.

The frame members It! and [2 also comprise rear runs connected. to the central runs below the bottom of the model, and extending heightassaees 3 wise and .rearwardly-betweenitheskerfi 44 and'the rearmost point of; the;bot-.tm:of: the; model.- 'Iihe shape.- and arrangement; of; the; runs of the mom:- bers- Ill and: I-2- insures unobstructed: visibility, from one. side of? the-modeh of: points; along, its bottom at the heel end, breast line; ball and toe endr whereby the relation of these points toa gage or template fortesting 'the, bottom profile of the. modelcan readily be, observed;

After the kerfs 4 21' and 44 .haveybeenmade as described above,,the toe and, heel portions of. the model are-moved relativelyto thgmid portion of the model to correct its toe spring: and: wedge angle. this correction being: ind-icatetlv in; Fig. 2 by the angle bet-ween the. full and dottedlines indicating. the bottom. profile of; the toe and heel portionsof the modelintheiu corrected and original positionsrespectively.

The toe spring oithe; model is; corrected by adjusting: a: screw 45: threadedin a; slide as and carrying at its, lower end a pad 5.0. 'Ifhe padis connected to the screw by a ball and socket joint which permits the pad to seat. itself on whateyer portion of. the modelitengagesq. The; slide 48.: is adapted tobemoved lengthwise; of' the last in a slot 5.1 formed in the strut, |3.:170-b13ingthe pad 50 over the toe endof. the model regardless of its length.

Another screw 52 at. theheel. end of the device for correcting the wedge angle of the model. is threaded in the strut l4 and is operable to=move a. bar 54 toward or away from the heel portion of the model. Thescrew 5.2 is arranged to rotatefreely in the'ba-r 5.4 and, is held: in the. latter by a pin 56 which is fixed in. the bar 54 and; re

ceived. in: a peripheral groove; formed in the screw 52. A pair of. screws 58 fixed; on, each end. of the bar 54 are receivedin slots 59; in the frames. Ill and I2, thereby to guide the bar 54a-xially of the screw 52. I

Ordinarily, in the use of the illustrated device, the screws 46 and 52 are set up so as to cause the open ends of the kerfs 42 and 44 to be closed, although if a lesser movement of the toe and heel portions of the model is adequate to provide the required correction, the operator may make a corresponding smaller adjustment. If, upon measuring the model, the toe spring and wedge angle are found to be correct, the toe and heel portions of the last are next permanently secured to the mid portion while they are held in their corrected positions by the screws 46 and 52. If the measurement of the model indicates that the correction permitted by closing a kerf formed by only one saw cut is inadequate, the model is again presented to the saw, the original kerf being closed completely or to a lesser extent depending upon the required degree of correction. It thus is possible by the use of the illustrated device to increase the width of a kerf by predetermined amounts depending upon whether the original kerf is partially or entirely closed before the second out is made. As a result of this procedure the operator is enabled to cut away such an amount of the model that when the required correction is made portions of the model at opposite sides of the kerf will be firmly seated on each other thereby insuring rigidity in the connection between the mid portion of the model and its toe or heel portions.

The permanent fastening of the end portions of the model to its mid portion is also efiected while the portions of the model are held in the device in their corrected relation. The first step in this procedure consists in drilling holes adapted: to :receive screw fastenings, the headsv of which are sea-ted in the toe and heel portions of the model and thethreadedwportions of which engage the mid portion of the model. As herein illustrated each. screw fastening 66 is inserted in a bore or hole the difierent sections of which in the different portions of the model are. coaxial. Each bore comprises a section 6| large enough to. accommodate the head of the fastening 60, asomewhat smaller section 62 adapted to receive the shank of the fastening, this section extending through the kerf. A third and still smaller sec-.

ti'on 64. of the bore is formed in the mid portion of the model so as to facilitate the setting of the fastening; and to avoid splitting of the model.

.It will, now be understood that because the DQItiOI s of the model are held in their corrected relation in the present device when the bores 62 and 64 aremade and the fastenings 66 are driven, these borescan; readily be formed in exact coaxial relationand of such size as closely to receive the fastenings thereby eliminating any tendency for the fastenings to become jammed as they are driven and insuring a rigid connection between the; portions of the model.

The novel method for correcting last models disclosed herein has not been claimed in the present application since it forms the subject-matter of av copending application Serial No. 480,504 filed in our names on March 25, 1943.

Having described ourinvention, what we claim as new and desire to secure by Letters Patent of the United States, is:

1. Ina last model correcting device, a frame, means for securing therein a model to, be corrected, said frame comprising members disposed at opposite sides of said model and extending alternatelylengthwise and heightwise of the model, said: members being shaped and. arranged to perunit transverse kerfs to be cut. in the. model partialiy separating heel and toe portions of the model; from the mid portion thereof and to afiord visibility of the bottom of the model when viewed from one side at the heel end, breast line, ball line and toe tip, and means for moving the portions of the model relatively to each other to correct the bottom profile of the model.

2. In a last model correcting device, a frame comprising means for clamping therein a model which is to have transverse kerfs formed therein partially separating heel and toe portions of the model from its mid portion, said frame being shaped and arranged to extend along a side of the model from above the toe portion of the model heightwise of the mid portion of the model between said kerfs and thence heightwise and rearwardly of the heel portion of th model between the rearmost kerf and the rear extremity of the bottom of the model, and means mounted at the ends of said frame for moving the heel and toe portions of the model relatively to the mid portion thereof to correct the bottom profile of the model.

3. In a last model correcting device, a frame comprising a central run arranged to extend heightwise of the mid portion of a model along a side thereof and carrying means for clamping the mid portion of the model thereon, and a rear run extending heightwise of the model between its heel end and breast line, said runs being connected below the bottom of the model and being spaced longitudinally of the model to permit a transverse kerf to be cut therein partially separating a heel portion of the model from its mid portion whereby the heel portion may be swung about the unsevered section of the model to correct the wedge angle, and means mounted on said rear run for holding the heel portion of the model in its corrected position.

4. In a last model correcting device, a frame comprising a central run arranged to extend heightwise across the mid portion of a model and carrying means for clamping the mid portion of the model thereon, a rear run extending heightwise of the model between its heel end and breast line and thence rearwardly of the model above its bottom, said runs being connected below the bottom of the model and spaced longitudinally of the model to permit a transverse kerf to be cut therein partially separating a heel portion of the model from its mid portion, and a member mounted on said rear run for adjustment lengthwise of the model to correct its wedge angle, said member being arranged to engage the heel end of the model and to hold the heel portion in it corrected position relatively to the clamped mid portion of the model.

5. In a last model correcting device, a frame comprising means for securing therein a model to be corrected, said frame comprising a central run extending heightwise of the mid portion of the model and beyond its top and bottom surfaces, said run being totally included between planes defining kerfs to be out in the model partially to separate heel and toe portions of the model from the mid portion thereof, said frame having a rear run extending heightwise of the model between its heel end and breastline, the width of said rear run being substantially less than the length of the heel seat of the model, said runs being connected below the bottom of the model, each of said runs having terminal por tions extending lengthwise of the model above its bottom, and means mounted in said terminal portions operable to move the heel and toe portions of the model relatively to the mid portion thereof to correct the bottom profile of the model.

6. In a last model correcting device, a frame having a guiding surface, means carried by said frame for clamping therein a model to be corrected, said clamping means comprising a member adapted to engage a positioning surface on said model extending transversely thereof parallel to its bottom, said member being substantially perpendicular to said guiding surface, said frame being shaped and arranged to permit the unobstructed access of portions of the model at each end of its mid portion to a saw movable through a table on which said guiding surface rests, thereby to form kerfs in the model partially separating toe and. heel portions of the model from its mid portion, and means mounted on said frame for relatively moving the portions of the model with respect to each other to correct the bottom profile of the model.

7. In a last model correcting device, a frame comprising parallel members spaced to receive therebetween a last model having a jig hole in its mid portion extending transversely thereof and parallel to the bottom of the model, a support adapted to be received in said jig hole and extending between said fram members perpendicular thereto, a clamp cooperating with said support to hold the model in said frame, the bottom of the model being perpendicular to said frame members,said frame membersbeing shaped and arranged to permit the unobstructed access of portions of the model before and behind its mid portion to a saw, thereby to form kerfs partially separating the heel and toe portions of the model from its mid portion, and members mounted on said frame for movement into engagement with the ends of the model for moving and holding the toe and heel portions thereof relatively to the mid portion so as to correct the bottom profile of the model.

OSCAR S. PORTER. LEO A. CARRELL. 

